By-pass failing removeUnusedImports step at Java 9 builds

See diffplug/spotless#83 for details.

.travis.yml

@@ -1,36 +1,27 @@
 language: java
 
-sudo: required
-
-# required for oraclejdk9
+sudo: false
 dist: trusty
 
 jdk:
-  - oraclejdk8
+#  - oraclejdk8
   - oraclejdk9
 
 addons:
   apt:
     packages:
-      - oracle-java8-installer
+#      - oracle-java8-installer
+      - oracle-java9-installer
 
 matrix:
   allow_failures:
     - jdk: oraclejdk9
 
-before_cache:
-  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
-  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
-
-cache:
-  directories:
-    - $HOME/.gradle/caches/
-    - $HOME/.gradle/wrapper/
-
 # Display Gradle version instead of letting Travis execute './gradlew assemble' by default
 install: ./gradlew -version
 
 script:
   - java -version
   - ./gradlew -version
-  - ./gradlew --refresh-dependencies clean check -Dscan
+  - export GRADLE_OPTS=--add-opens java.base/java.lang=ALL-UNNAMED
+  - ./gradlew --stacktrace clean check

build.gradle

@@ -385,7 +385,10 @@ subprojects { subproj ->
 			licenseHeaderFile headerFile, '(package|import) '
 			importOrderFile rootProject.file('src/eclipse/junit-eclipse.importorder')
 			eclipseFormatFile rootProject.file('src/eclipse/junit-eclipse-formatter-settings.xml')
-			removeUnusedImports()
+
+			if (org.gradle.api.JavaVersion.current() == org.gradle.api.JavaVersion.VERSION_1_8) {
+				removeUnusedImports()
+			}
 
 			trimTrailingWhitespace()
 			endWithNewline()